This invention relates to use of dense phase fluids in combination with dense phase fluid modifiers as solvents for removal of polymers and photoresist materials used in the manufacture of semiconductor wafers or chips.
During manufacture of integrated circuits, commonly referred to as semiconductor chips or microchips, several iterations of a photolithographic process are used. In this manufacturing process, dielectric, barrier or electrically conducting layers such as silicon dioxide, silicon nitride or metal is first deposited upon a substrate such as a silicon or gallium arsenide wafer by any of several suitable processes such as thermal oxidation, chemical vapor deposition, sputtering, ion implantation or vacuum evaporation.
After formation or deposition of the dielectric, barrier or conducting layer, a photoresist material is applied to the wafer by any suitable means including, but not limited to, spinning of the wafer to distribute liquid photoresist evenly on the surface of the wafer.
Usually the photoresist material coated wafer is then heated in a xe2x80x9csoft bakexe2x80x9d or prebake step to improve adhesion of the photoresist material to the substrate surface and/or the barrier layer and to remove solvent from the generally polymeric photoresist material.
After the photoresist is soft baked onto the barrier layer, portions of the soft baked photoresist coated wafer are selectively exposed to high energy light such as high intensity ultraviolet light in a desired pattern defined by a photomask. Developing agents are then used to develop the portions of the photoresist material which were exposed to the high energy light.
When positive photoresist materials are used, the developed portions of the photoresist materials are solubilized by the exposure to the light and development and then are washed away, leaving portions of the dielectric or conducting layer coated wafer exposed and other portions of the wafer coated with dielectric or conducting layer underneath the remaining, unexposed and undeveloped photoresist layer.
Conversely, when negative photoresist materials are used, the undeveloped portions of the photoresist materials are selectively removed for exposing selected portions of the barrier material coated substrates in the desired patterns.
Once the pattern of photoresist has been established on the wafer, the wafer is xe2x80x9chard bakedxe2x80x9d to densify and toughen the photoresist material and improve adhesion to the dielectric or conducting layer. The exposed substrate and/or barrier material is then etched (removed) by any of several suitable methods, depending upon which materials were used as the dielectric or conducting layer. Wet chemical etching, dry etching, plasma etching, sputter etching or reactive-ion etching processes may be used. The etching processes remove barrier material which is unprotected by photoresist, leaving both portions of bare wafer and portions of wafer having layered coatings of barrier layer and the photoresist material which protected the barrier layer underneath from the etching process on the surface of the wafer.
The wafer having on its surface the pattern of dielectric or conducting layer material coated with photoresist material is then treated in an aggressive step to remove the hard baked photoresist material from the remaining pattern of barrier layer material. This has traditionally been done using solvent washes of halogenated hydrocarbons, mixtures of sulfuric acid and hydrogen peroxide, or highly alkaline mixtures of hydroxides with activators. Use of any of these solvent mixtures produces high volumes of undesirable liquid waste streams.
After removal of the hard baked photoresist material, in a final step, the substrate with the patterned surface layer on it is washed with deionized water to ensure that all traces of photoresist removal solvents are removed from the wafer surface.
This photolithographic process is repeated as many times as needed to produce as many layers of different patterns of dielectric, barrier or conducting layer material upon the substrate as desired. Layers of either positive or negative photoresist material can be used in various combinations on the same wafer.
There is a need for methods for effectively removing photoresist materials in ways that reduce the amount of undesirable waste streams.
Therefore it is an object of this invention to provide a method of removing photoresist materials used in the manufacture of integrated circuits or other electronic components such as circuit boards, optical waveguides and flat panel displays.
It is another object of this invention to provide a method of reducing undesirable waste streams produced during manufacture of integrated circuits or other electronic components.
It is also an object of this invention to provide a method of manufacturing integrated circuits which eliminates the need for the final aqueous rinse step.
It is a further object of this invention to provide solvents useful for dissolving polymers used as photoresist materials.
It is yet another object of this invention to provide an apparatus for removing photoresist materials from substrates for integrated circuit or other electronic components.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. The claims appended hereto are intended to cover all changes and modifications within the spirit and scope thereof.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, a combination of at least one dense phase fluid and at least one dense phase fluid modifier is used to contact substrates for electronic parts such as semiconductor wafers or chips to remove photoresist materials which are applied to the substrates during manufacture of the electronic parts. The dense phase fluid modifier is one selected from the group of cyclic, aliphatic or alicyclic compounds having the functional group: 
wherein Y is a carbon, oxygen, nitrogen, phosphorus or sulfur atom or a hydrocarbon group having from 1 to 10 carbon atoms, a halogen or halogenated hydrocarbon group having from 1 to 10 carbon atoms, silicon or a fluorinated silicon group; and wherein R1 and R2 are substituents selected from the group of hydrogen, hydrocarbon groups having from 1 to 10 carbon atoms, halogen, and halogenated hydrocarbon groups having from 1 to 10 carbon atoms, silicon, fluorinated silicon groups; and wherein R1 and R2 can be the same or different substituents; and wherein, as in the case where Y is nitrogen, R1 or R2 may not be present.
The invention compositions generally are applied to the substrates in a pulsed fashion in order to remove the hard baked photoresist material remaining on the surface of the substrate after removal of soft baked photoresist material and etching of the barrier layer.